A canvas stretcher, also known simply as a “stretcher” is a frame which can be constructed in various manners and of various materials and which is utilized for mounting and properly tensioning canvas sheet material (such as, for example, paintings). The variations in stretcher design most commonly involves corner construction. Manufacturers of stretcher frames have traditionally assembled such from custom prepared corner and straight frame elements. Such assembly has required the production and use of both corner and straight frame (also known as “perimeter”) members. Such production has required, in many instances, the preparation of mortised joints utilized for joining corner members to straight members, as well as similar joints utilized to form corners from, most often, two separate parts. In certain instances, pre-formed corner members have been utilized by such manufacturers so as to eliminate the need for preparing a mortised joint on the ends of such corners at the point and place of frame assembly, while still requiring such joinery to be performed upon perimeter members. Corner members utilized in such stretcher frames may be adjustable or non-adjustable.
An example of an adjustable corner is provided in what is commonly referred to as a “French” stretcher. Such stretcher frames include corners formed from two interlocking, but separable parts each having a 90 degree and 45 degree end. More specifically, such two piece corners include a mortised channel and assembly tine which provides a means for joining the two pieces which form each corner. Specifically, each of the two corner sections is attached to one another along a 45 degree end and, once affixed via the aforementioned mortised joint, from a 90 corner for the stretcher frame. Each end of the assembled corner is attached to a straight frame member at the 90 degree end of the corner sections so that when four corners are affixed to four straight frame member, a rectangular or square frame is formed. The straight members are affixed to the corner by any suitable means such as, for example, metal fasteners, glue, slots and tines or any other suitable means for forming a permanent joint. Mortised joints are preferred due to their strength and stability. Once assembled, the joint formed between each straight member and each corner is, in regard to a French stretcher, a fixed joint. However, the corners are assembled with an adjustable joint and so provide a means of adjusting the distance between each of the two sections making up each corner.
The mortised slot and tine assembly utilized to assemble a French stretcher corner includes an open, converging space adjacent to the slot which is commonly referred to as a keyway. An adjustment key, urged into such keyway, acts to open up a space between the two sections forming the corner. When such an adjustable corner is utilized in a quadrilateral (commonly square or rectangular) frame, insertion of a key into the keyway increases the space, not only between the two sections of the adjusted corner, but also increases the space between the two straight (perimeter) members stretcher affixed to either end of the corner. As discussed in more detail, below, the increase distance between perimeter members caused by the opening of one or more corners increases the perimeter dimension of the frame.
A canvas painting, for example, mounted upon a French stretcher frame, may be so mounted via, staples, screws or tacks to the back face of the perimeter and corner members forming the frame. Such canvas paintings are initially mounted at a preferred tension so as to properly display a relatively flat canvas without strain. However, over time, the canvas tends to sag as the dimensions of the material change, due, in large part, to changes in moisture content as well as changes in the canvas material structure itself. The aforementioned adjustable corners of a French stretcher enables simple re-tensioning of such a sagging canvas painting when required by simply adjusting, via key insertion, the perimeter dimension of the frame to which the canvas is affixed.
Besides the above-described adjustable corners, canvas stretchers may also utilize corners that are not, in fact, separable or otherwise adjustable. Such stretchers may achieve re-tensioning of a canvas by simple re-mounting the material to the frame in a more taught manner. On the other hand, other canvas stretchers provide frame adjustment without altering corner spacing. Such frames may utilize a corner which is assembled via a fixed (non-separable) joint, and provide adjustment by creating a space between the ends of the corner abutting perimeter members.
For example, the stretcher disclosed in U.S. Pat. No. 8,307,880 (THE “880 patent”) stretcher, provides adjustment of frame size without including an adjustable corner. The stretcher disclosed in the '880 patent teaches the use of a two piece corner that is permanently assembled into a non-adjustable fixed corner piece. However, the '880 stretcher provides frame adjustment by affixing an adjustable screw to a fixed slot formed at a discrete and single location within the inside edge of perimeter sections adjacent to the each end of each such straight frame element. The '880 stretcher affixes the disclosed fixed corner to perimeter members by means of dowel pins and inserts. However, the joint formed between each straight member and corner is not permanently fixed. The screw type device of the '880 patent provides a means of adjusting the distance between each perimeter member (straight member) and the corner member to which it is attached. When the adjustment screw is rotated, the end thereof is advanced towards and against a force block extending from the corner. Contacting and biasing the adjustment screw against the force block partially separates the perimeter member to which the adjustment screw is attached from the corner. This separation, in turn, increases the perimeter dimension of the stretcher so as to apply tension to a canvas sheet affixed to the frame.
As mentioned above, pre-formed stretcher corners are well known to the industry and may be commonly utilized by commercial manufacturers. Such component parts enable ease of handling and shipment of stretcher materials prior to reaching the point of final assembly into a frame. Such pre-formed corners may be provided in either an adjustable or fixed configuration. Stretcher frames must be manufactured in varying sizes and shapes—such as rectangular or square—in order to be applicable to the various dimensions of the canvas they are designed to mount and stretch. In order to attain a perimeter dimension and shape (most often, rectangular or square) required for any given canvas, the perimeter members comprising the frame may be formed or cut to an appropriate length. Utilization of prepared corners, including adjustable French style corners, is of great assistance in the preparation of such frames since such corners may be provided with pre-formed mortised ends for quick assembly to perimeter members. However, regardless of the availability of such pre-formed corners, perimeter members whether pre-formed or not, often require cutting to a specific length and the point and location of frame assembly in order to provide a frame of a desired perimeter dimension. The cutting of a pre-formed perimeter member will, of course, eliminate any mortise joint preparation located at the end of the perimeter member being cut. Although it might be possible to assemble a stretcher frame from both pre-formed and mortised corner and pre-mortised perimeter members, such would obviate the production of custom sized frames have a perimeter dimension other than the one provided by the stock perimeter members—without having to reproduce the joinery cut off the end of the perimeter member after cutting same to provide the desired frame dimensions.
It would be highly beneficial if pre-formed stretcher components could be disclosed, as well as a method for forming a custom sized stretcher frame, that would allow for the production of frames of any desired perimeter dimension, without the need for performing additional joinery upon one or more ends of the perimeter members requiring cutting in order to produce such custom sized frames.
The most time consuming and labor intensive portion of custom stretcher production is the preparation of the mortised joints which are prepared at each end of the perimeter member. However, such mortised joints, as opposed to a joint which is simply nailed, screwed or glued, provides the stable joint required between the perimeter and corner members of a custom stretcher. There is also much time devoted to placement and affixation of cross member supports along the inside edges of the perimeter members to which they are affixed.
It would be highly advantageous if pre-formed corner and perimeter members were disclosed which enabled one to quickly and easily assemble a canvas stretcher of a desired perimeter dimension—having adjustable corner members—, without having to perform, joinery upon the end of each perimeter member requiring custom cutting prior to assembly. It would be further advantageous if such a custom canvas stretcher kit could be provided which enabled quick and simple affixation of cross bars to the frame without having to perform further joinery upon perimeter members or the cross bar(s) after custom cutting of same.